CURRENT-DRIVEN ELECTROMAGNETIC MODES

The dispersion relation for current-driven electromagnetic instabilities in an inhomogeneous slab geometry is derived and analyzed. It is shown that current in the direction of the equilibrium magnetic field, as well as transverse current gradients can strongly modify the drift-Alfven dispersion relation as given by Kadomtsev (1965). If the perpendicular wavelength is much larger than the ion gyro-radius there can be fluid-like instabilities resulting from the interaction of the density gradient and current gradient with the parallel current. It is shown that weak parallel electron currents can produce instabilities which are stronger than the finite gyro-radius, density gradient and parallel flow shear instabilities previously derived by Dobrowolny (1972). Applications to finite beta plasmas are discussed.